<PAGE>
EXHIBIT 23.1
INDEPENDENT AUDITORS' CONSENT
We consent to the incorporation by reference in this Registration Statement
of Tetra Tech, Inc. on Form S-3 of our reports dated November 15, 2000,
appearing in and incorporated by reference in, the Annual Report on Form 10-K of
Tetra Tech, Inc. for the year ended October 1, 2000, and to the reference to us
under the heading "Experts" in the Prospectus, which is part of this
Registration Statement.
/s/ Deloitte & Touche LLP
Los Angeles, California
December 29, 2000
